1. Field of the Invention
The present invention generally relates to electrostatic electron beam phase control, more specifically to microfabricated (also known as micromachined) electrostatic electron beam phase control, and still more specifically to micromachined electrostatic electron beam phase control in an electron microscope for contrast enhancement.
2. Description of the Relevant Art
A standard way that people currently address the problem of producing usable amounts of image contrast for weak phase objects is to operate an electron microscope in a substantially out-of-focus condition. This practice only produces a significant amount of contrast over a limited range of spatial frequency, also known as resolution. At resolutions both below and above a selected range, however, the contrast either remains weak or oscillates undesirably from positive to negative contrast.
A less standard approach for contrast enhancement, which is apparently not yet used in practice, is to shift the phase of the scattered electrons relative to the unscattered beam by placing a thin film of uniform thickness (of an appropriate material, such as carbon) at the back focal plane, with a small hole in the center for the unscattered beam. This approach is partially effective, but comes at the cost of losing about ⅓ of the scattered electrons, because these are scattered a second time by the thin film.
The publication “Uber die Kontraste von Atomen im Elektronenmikroskop” by Hans Boersch, Jun. 18, 1947, which is hereby incorporated by reference in its entirety, relates to electron microscope contrast.
The publication “LIGA Micromachining and Microdevices Using Deep Etch X-ray Lithography at Beamline 3.3.2” by Boehme and Wiberk, undated, which is hereby incorporated by reference in its entirety, relates to LIGA micromanufacturing.
The publication “Intro to electron optics” located at http://www.bio.umass.edu/microscopy/technai/tem/eointro.htm, which is hereby incorporated by reference in its entirety, relates to electron optical systems.
The publication “Particle-Particle Interaction Effects in Image Projection Lithography Systems” by S. D. Berger, D. J. Eaglesham, R. C. Farrow, R. R. Freemean, J. S. Kraus, and J. A. Liddle of AT&T Bell Laboratories, Murray Hill, N.J., which is hereby incorporated by reference in its entirety, relates to electron Coulomb interactions.
The publication “Aberration Correction In Electron Microscopy” by the Material Science Division of Argonne National Laboratory, Jul. 18-20, 2000, which is hereby incorporated by reference in its entirety, relates to improvement in aberrations in electron microscopes.
The publication “Electron interference: mystery and reality” by Hannes Lichte, Dresden University, Mar. 28, 2002, which is hereby incorporated by reference in its entirety, relates to electron interference effects.